Bulb



FIG. 1 is a perspective view of the bulb embodying the new design;

FIG. 2 is a front elevational view thereof, the rear elevational view, right side elevational view and left side elevational view being identical thereto;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a bottom plan view thereof. 

The ornamental design for bulb, as shown and described. 